The trapezoidal metric thread form is similar to the Acme thread form, except the thread angle is 30°.It is codified by DIN 103. While metric screw threads are more prevalent worldwide than imperial threads for thread forms, the imperially sized threads predominate in the trapezoidal thread form.
ISO 262 selected sizes for screws, bolts and nutsNominal diameter (mm) | Pitch (mm) | Nominal diameter (mm) | Pitch (mm) | 1st choice | 2nd choice | Coarse | Fine | 1st choice | 2nd choice | Coarse | Fine | 1 0.250.216 21.51.2 0.250.2 182.52 or 1.5 1.40.30.220 2.52 or 1.51.6 0.350.2 222.52 or 1.5 1.80.350.224 322 0.40.25 27322.5 0.450.3530 3.523 0.50.35 333.52 3.50.60.3536 434 0.70.5 39435 0.80.542 4.536 10.75 454.53 710.7548 538 1.251 or 0.75 525410 1.51.25 or 156 5.5412 1.751.5 or 1.25 605.54 1421.564 64
ISO 262 selected sizes for screws, bolts and nutsNominal diameter (mm) | Pitch (mm) | Nominal diameter (mm) | Pitch (mm) | 1st choice | 2nd choice | Coarse | Fine | 1st choice | 2nd choice | Coarse | Fine | 1 0.250.216 21.51.2 0.250.2 182.52 or 1.5 1.40.30.220 2.52 or 1.51.6 0.350.2 222.52 or 1.5 1.80.350.224 322 0.40.25 27322.5 0.450.3530 3.523 0.50.35 333.52 3.50.60.3536 434 0.70.5 39435 0.80.542 4.536 10.75 454.53 710.7548 538 1.251 or 0.75 525410 1.51.25 or 156 5.5412 1.751.5 or 1.25 605.54 1421.564 64
Coefficient of friction for thrust collarsMaterial combination | Starting {displaystyle mu _{c}} | Running {displaystyle mu _{c}} | Soft steel / cast iron0.170.12Hardened steel / cast iron0.150.09Soft steel / bronze0.100.08Hardened steel / bronze0.080.06